The present invention relates to a rotary rock drilling machine, especially for expansion drilling. More particularly, it relates to a rotary rock drilling machine which has a carriage, a rotary drilling drive arranged longitudinally displaceably on the carriage, a guiding head for a drilling rod on a head end of the carriage, and a screw drilling rod composed of a plurality of releasably connectable drilling rod parts. The drilling rod parts have a multi-cornered coupling pin with a snap pin on one hand and a multi-cornered coupling bush with an engaging opening for the snap pin on the other hand. In the guiding head a positioning device is arranged for arresting the rotary position of the drilling rod, and an unlocking device is provided for the snap pin.
Rotary rock drilling machines of the above mentioned general type are known in the art. One of such rotary rock drilling machines is disclosed in the German document DE-OS 2,834,151. Here the positioning device is shown in FIG. 4 in connection with FIG. 1 and formed as a relatively light pin which is welded on the drilling rod and cooperates with a turnable-in abutment in the guiding head. As long as the pin is located completely in engagement and contact with the abutment, the unlocking device can be turned into operation and the snap pin for separating the coupling pin of one drilling rod part from the coupling bush of another drilling rod part is displaced. This positioning device, in addition to the danger of a return springing of the pin from the abutment, possesses the disadvantage in that the wide-surface pin hinders the rock movement between both neighboring convolutions, thereby reduces important transporting output of the drilling rod in the expansion drilling machine. Moreover, there are also difficulties in that the turned-in abutment can collide with the rotatable screw convolutions. This disadvantage was recognized by the applicant and he removed the convolutions located near the pin, which undesirably affects the continuity of the rock transportation.
In the second alternative shown in FIG. 7 of the above mentioned patent, in a kinematic reverse the pin is arranged on the guiding head of the rotary rock drilling machine while the abutment is formed by a restoring spring which considerably reduces the cross-section of the coupling bush. The restoring spring of the coupling bush reduces the effective required cross-section for the torque transmission so dramatically that a breakage is unavoidable. This is true especially for the tendency of increasing the drive output double or triple the conventional drive outputs in the known expansion drilling machines which are characterized for this field. This embodiment is not suitable for transmitting such torques.
The German document DE-OS 2,733,028 discloses an arrangement on a rotary rock drilling machine with an unlocking device for the rear snap pin, which is placed into the drive pin and actuated by a fluid-operated piston arranged in it or in the drive shaft. This complicated unlocking device has the disadvantage of using pressure fluid supply in the drive shaft. Correspondingly it is susceptible to disturbances. Moreover, this system is not suitable for drilling machines which frequently required supply of a drilling rinsing through the drive shaft.
Finally, another expansion drilling machine is disclosed in the German document DE-PS 2,654,748. In this machine an undesirable rotation of the drilling drive is prevented in that an abutment is pressed by a cylinder against a "surface" of the drilling motor-insertion end. The "surface" here is a flattening of the round collar on the rear end of the insertion end. Such an arresting can prevent an undesirable rotation, however, it cannot hold the rotary drilling drive in the rotary position which is definite for the coupling and unlocking steps. This patent does not disclose how the turning-in or driving-in of the insertion end and the whole drilling strand can be brought in the accurate rotary angular position. An unlocking assumes always an exact positioning, since otherwise the unlocking arrangement can not be turned into operation.
The known expansion drilling machines exhibit the attempts to mechanize the adjustment process of the drilling rods and possibly to automate the same. In every case only partial results are achieved. In particular, the reaching of the rotary position of the drilling drive or the drilling rod strand was not mechanized at all or mechanized only with disadvantages for the feed capacity and for relatively weak drives. The last mentioned point is especially grave since the drive outputs and torques are increased in the expansion drilling machines up to 2-3 times. Moreover, expansion drilling machines are predominantly driven by pressure air motors which have massive rotors rotating at high speeds and are especially difficult to brake.